1. Technical Field
The present invention relates to angular rate sensors and electronic devices.
2. Related Art
Information devices, such as, digital cameras and car navigation systems carry an angular rate sensor in order to prevent blurring of images due to hand movement or to detect the position of a vehicle. As the angular rate sensor, for example, a 32 kHz tuning-fork quartz oscillator is still used as it can utilize the existing design resource and energy saving properties. However, when forming a 32 kHz tuning-fork quartz oscillator, the length of the prongs of the tuning fork becomes as large as several millimeters, whereby the entire length including the package becomes as large as almost 10 mm.
In recent years, piezoelectric vibration devices that use a driving section having a piezoelectric thin film interposed between upper and lower electrodes and formed on a silicon substrate, instead of quartz, have been developed. Known structures of such piezoelectric vibration devices include a beam type structure (see FIG. 1 of JP-A-2005-291858) and a structure having a tuning fork vibration device formed with two beams (see FIG. 1 of JP-A-2005-249395) are known. When utilizing such piezoelectric vibration devices, since the thickness of a silicon substrate can only be reduced to about 100 μm, the prong length of the beams may become as much as several millimeters or greater in order to obtain a resonance frequency at several tens kHz. This makes it difficult to reduce the size of the angular rate sensor having such a piezoelectric vibration device.